[pgjdbc/pgjdbc] c6ae21: Update Contributing.md

  Branch: refs/heads/davecramer-patch-3
  Home:   https://github.com/pgjdbc/pgjdbc
  Commit: c6ae210d8a980192a08d6fab92ff39bb53121ace
      https://github.com/pgjdbc/pgjdbc/commit/c6ae210d8a980192a08d6fab92ff39bb53121ace
  Author: Dave Cramer 
  Date:   2018-07-20 (Fri, 20 Jul 2018)

  Changed paths:
    M CONTRIBUTING.md

  Log Message:
  -----------
  Update Contributing.md

After reading this I realized it was a bit dated.
I've also attempted to massage the grammar.



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